Question

How will you obtain pure potassium permanganate (${\text{KMn}}{{\text{O}}_{\text{4}}}$​) crystals from its ore, pyrolusite? Give the steps involved and the corresponding reactions.

Answer 1

The mineral ore of potassium permanganate (${\text{KMn}}{{\text{O}}_{\text{4}}}$​) crystals is pyrolusite. The ore contains the manganese dioxide as the core chemical. The extraction process involves two steps to obtain pure potassium permanganate (${\text{KMn}}{{\text{O}}_{\text{4}}}$​) crystals.

Complete step by step answer:
Pyrolusite is a manganese dioxide mineral ore with the molecular formula {\text{Mn}}{{\text{O}}_{\text{2}}}.
We know that pure potassium permanganate (${\text{KMn}}{{\text{O}}_{\text{4}}}$​) crystals can be extracted from the ore in two steps described below:
Step 1: Pyrolusite ore is converted to potassium manganate (${{\text{K}}_{{\text{2}}}}{\text{Mn}}{{\text{O}}_{\text{4}}}$)
The first step is where manganese dioxide gets fused with potassium hydroxide (${\text{KOH}}$) in the presence of oxygen to form potassium manganate. The chemical reaction is represented as below:
${\text{2 Mn}}{{\text{O}}_{\text{2}}}{\text{ + 4 KOH + }}{{\text{O}}_{\text{2}}}\xrightarrow{{{\text{Heat}}}}{\text{ 2 }}{{\text{K}}_{{\text{2}}}}{\text{Mn}}{{\text{O}}_{\text{4}}}{\text{ + 2 }}{{\text{H}}_{\text{2}}}{\text{O}}$
We can see that in this step 2 mole of manganese dioxide reacts with 4 moles of potassium hydroxide to produce 2 moles of potassium manganate and 2 moles of water molecule as by-products.
Step 2: Oxidation of potassium manganate (${{\text{K}}_{{\text{2}}}}{\text{Mn}}{{\text{O}}_{\text{4}}}$) to into potassium permanganate (${\text{KMn}}{{\text{O}}_{\text{4}}}$)
The last step is where potassium manganate formed in step 1 is converted into potassium permanganate through oxidation in the presence of chlorine. The chemical reaction is represented as below:
${\text{2}}{{\text{K}}_{\text{2}}}{\text{Mn}}{{\text{O}}_{\text{4}}}{\text{ + C}}{{\text{l}}_{\text{2}}} \to {\text{2KCl + KMn}}{{\text{O}}_{\text{4}}}$
We can see that in this step 2 mole of potassium manganate reacts with one mole of chlorine to produce one moles of potassium permanganate and 2 moles of potassium chloride (${\text{KCl}}$) as by-products.
Finally, after crystallisation and drying the pure potassium permanganate is obtained from the pyrolusite ore.

Note:
The potassium permanganate also known as Condy’s crystal is purple in colour. This compound is soluble in water. The potassium manganate is dark green in colour. The major application of it is a very good oxidising agent and used in synthesis of various organic compounds.